On Tuesday evening, while part of the New York art world is uptown bidding at Sotheby’s, another part will be gathered at the Riverfront Pavilion Midtown on the West Side, spending their money on a more charitable cause. The event is a $50,000-a-table gala honoring contemporary American artists, and the guests will include many major New York arts patrons, including the chairman of the Whitney Museum of American Art and several prominent board members of the Museum of Modern Art.

But the beneficiary of Tuesday night’s high-rolling event isn’t a New York institution. It’s Britain’s Tate museum.

The group behind Tuesday’s gala is the American Patrons of Tate, a charity founded in 1988 with the goal of raising funds for the Tate to acquire American art. In the past few years, the group has attracted significantly more attention from the art community: In fiscal year 2005, it raised $1.01 million in contributions, according to documents filed with the IRS. In 2000, it raised only $237,270; in 1999, a paltry $50,125.

This year, one of the trustees, Lady Lynn Forester de Rothschild, called in some favors, so the American Patrons of Tate were able to offer guests at the gala some unusual perks: an invitation to a cocktail reception in June with Prime Minister Blair and his wife, Cherie, and a group portrait taken by Annie Leibovitz, which, according to The Art Newspaper, will accompany an article about the group in Vanity Fair. (A spokeswoman for Vanity Fair confirmed that “we’re shooting the group,” but declined say when or whether an article was forthcoming.) The gala sold out immediately and is expected to raise $1.5 million. Among those attending will be Evelyn and Leonard Lauder, Ronald Lauder, Agnes Gund, and Mercedes and Sid Bass — all major collectors and cultural philanthropists.

Recently, however, the American Patrons of Tate attracted some less-flattering publicity. On February 24, at a panel at MoMA organized by the Art Dealers Association of America on “The Museum as Collector,” the director of the Solomon R. Guggenheim Museum, Lisa Dennison, raised the issue of competition among museums for fund raising and acquisitions. Addressing the Tate’s director, Nicholas Serota, who was sitting on the panel, Ms. Dennison described a threat from “a new phenomenon in the world, which is the American Friends of — the Tate, the Centre Pompidou, the Hermitage Museum.”

Ms. Dennison focused on the Tate group, in particular, referring to the invitation to Mr. Blair’s house and the photograph by Ms. Leibovitz: “These are compelling, compelling incentives that speak not of true philanthropy, but of ‘give us some money, give us some art, and we are going to give you something back that’s really, really enticing.'” She continued: “I know this because my board members come to me in deep conflict [saying,] ‘I want to be part of this group — I want to be a friend to the Tate, to the Centre Pompidou, to the Hermitage, to the Pushkin [Museum].’ What’s a poor American museum director to do?”

Some people involved with the American Patrons of Tate were surprised by Ms. Dennison’s comment and by the very public forum in which she made it. One of the trustees of the American Patrons of Tate, Ella Fontanals-Cisneros, suggested that Ms. Dennison didn’t understand the organization’s purpose. “Maybe Lisa said that not [understanding] that American Patrons of Tate works with a fund that was created by an Englishman in America, just to acquire American art” for the Tate, she said.

The president of the Pompidou group, called the Georges Pompidou Art & Culture Foundation, Robert Rubin, said he found Ms. Dennison’s comment, which was sent to him by a reporter in an email, revealing of the current level of competition for cultural philanthropy.

As to whether support for a European institution would foreclose or displace support for American ones, Mr. Rubin said, “It’s reasonable to expect that most advanced collectors will have multiple involvements. It’s a function of what they collect and which institutions they view as appropriate in the longterm as a repository for their collection. It’s not unreasonable to see collectors having simultaneous dialogues with several major institutions.”

Eli Broad, for example, is in the Pompidou Foundation and is also a trustee of MoMA, as well as of two major museums in Los Angeles, where he lives: the Museum of Contemporary Art and the Los Angeles County Museum of Art. In 2003, Mr. Broad gave LACMA $60 million for a new building.

On the other hand, Mr. Rubin noted, “if you’re talking about the neophyte … whose involvement may be fleeting or superficial, then there’s more competition –– especially if their interest is based on their ability to go to a gala and rub elbows with bold-faced names.”

Donald Marron, a vice chairman on MoMA board and a chairman of Tuesday’s gala, said, “The art world is global now, and all the leading institutions have relationships in one way or another. They collect many of the same artists, they try to share shows and collections,” he continued. “This is the result of the broader interest in art, but it’s also the result of the fact that good paintings are harder to find [and] more valuable.” He added that the Guggenheim, which has museums in Bilbao, Spain, Venice, and Berlin, and plans to open one in Abu Dhabi, “obviously has gone worldwide for a long time.”

Besides the groups alluded to by Ms. Dennison, “American Friends” groups include the American Friends of the Louvre, the American Friends of the Tel Aviv Museum of Art (which is having its own gala on Thursday, in order to raise funds for a new building), the American Friends of the British Museum, the American Friends of the Paris Opera and Ballet, the American Friends of the Donmar (a prominent London theater company), and the American Friends of the London Academy of Music and Dramatic Art.

The main function of these organizations is to allow Americans to make tax-deductible donations to institutions or charities outside America. That is completely legitimate according to IRS policy, an expert in not-for-profit law, Jeffrey S. Tenenbaum, said, as long as these groups operate in a particular way. “The U.S. charity has to offer ‘discretion and control’ over how the funds are utilized,” Mr Tenenbaum said, citing the IRS’s formulation. “It cannot just be a pass-through,” he continued “and you cannot tell donors that their money is just going [directly] to this museum.”

In that sense, “American Friends” groups tread a somewhat fine line. “If you look at their purpose clauses” when they file for 501(c)3 status, Mr. Tenenbaum said, “you can see that they’re artfully drafted to take advantage of the tax rules.” Many of them refer to their purpose as not simply to raise funds but to “raise public awareness” of the specified institution in America. The American Patrons of Tate’s purpose clause appears to bear little resemblance to the group’s current activities. It refers to sponsoring “exhibitions and loans of art works throughout the United States which would bring important British art to the attention of the United States public,” and to promoting “educational and scholastic exchange between the Tate Gallery in London and American art students and scholars.”

Asked in an e-mail message for examples of exhibitions of British art the group has sponsored in America, the director of American Patrons of Tate, Richard Hamilton, replied that the purpose clause was drafted in 1988, and “[w]hile we find that the majority of support is for American art, there are examples of individuals and foundations who wish to support British art at Tate.”

The more recently formed groups appear to step even closer to the line Mr. Tenenbaum described. The Web sites of the Donmar Warehouse and the London Academy of Music and Dramatic Art, for example, both direct Americans wishing to make tax-deductible donations to the addresses of their “American Friends” groups. The LAMDA Web site notes: “In order to facilitate tax-efficient gifts for our supporters, LAMDA has committed to establishing The American Friends of LAMDA — a separate organisation which can accept donations recognised as tax-deductible by the American Internal Revenue Service (IRS), with the primary aim to enrich theatre in the United States through encouraging a cross-cultural relationship.” There is a link to download the appropriate form; checks can be sent either to an address in New York, or straight to London.